Abstract
Wild bumblebees are key pollinators of crops and wild plants that rely on the continuous availability of floral resources. A better understanding of the spatio-temporal availability and use of floral food resources may help to promote bumblebees and their pollination services in agricultural landscapes. We placed colonies of Bombus terrestris L. in 24 agricultural landscapes with various degrees of floral resource availability and assessed different parameters of colony growth and fitness. We estimated pollen availability during different periods of colony development based on detailed information of the bumblebee pollen diet and the spatial distribution of the visited plant species. Total pollen availability did not significantly explain colony growth or fitness. However, when using habitat maps, the weight gain of colonies, the number of queen cells, and colony survival decreased with increasing distance from the forest. The better explanation of bumblebee performance by forest proximity than by (plant-inferred) pollen availability indicates that other functions of forests than pollen provision were important. The conservation of forests next to agricultural land might help to sustain high populations of these important wild pollinators and enhance their crop pollination services. Combining different mapping approaches might help to further disentangle complex relationships between B. terrestris and their environment in agricultural landscapes.
Highlights
IntroductionOf leading global crop types relying to varying degrees on pollination [1]
Animal pollination is crucial for around one third of worldwide food production, with 85%of leading global crop types relying to varying degrees on pollination [1]
We identified 45,900 pollen grains collected from 306 returning foragers of B. terrestris
Summary
Of leading global crop types relying to varying degrees on pollination [1]. In addition to domestic honeybees (Apis mellifera L.), wild bees greatly enhance and stabilize crop pollination, and they are often the most effective pollinators [2,3,4,5,6]. Habitat loss and intensive agricultural practices contribute to pollinator declines in different regions of the world [7], while the dependency of global agriculture on pollinators is increasing [8]. Supporting wild bees in agricultural landscapes is crucial to future economic and environmental stability [9,10]. Bumblebees are important wild pollinators that increase the yield of many crops, e.g., fruit trees, pepper, pumpkin, strawberries, and tomatoes [11,12]. The buff-tailed bumblebee (Bombus terrestris L.) is Agronomy 2020, 10, 1993; doi:10.3390/agronomy10121993 www.mdpi.com/journal/agronomy
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